Educational
Information:
Archaeological excavations and study of
fossilized remains and specimens of Kauri gum have suggested that
the Northland region may have supported vast kauri forests as far
back as 65 million years ago. The Lake Ohia area was supporting
such a forest about 30,000 years ago, well before the lake was
formed, when it is likely some sudden devastating event occurred
that sheared off the trees at ground level. The felled forest
became drowned by the lake and covered in silt which preserved and
eventually fossilized the remains.
The
cause of the devastating event remains open to speculation. Its
likely suddenness is suggested by some swamp preserved Kauri in the
wider region being unearthed with their leaves and cones still
green. In other places the tree trunks, buried deep in swamp mud
for thousands of centuries were found to all be lying in the one
direction.
Rapidly advancing ice sheets have been
suggested as a possible cause. Wind, flood, tidal wave, earthquake
or volcanic eruption are other possible causes.
Lake
Ohia was drained early in the 20th century to facilitate
Kauri gum digging. It was then that the visual effect of this
ancient forest emerged. Some evidence of the gum digging era
remains to the North east of Lake Ohia about 2km. up Inland Road.
Geocache GC 16VJB
(
Holey Moley By Gum) is located in this area.
Shallow water is present in Lake Ohia for
approximately 2 months of the year. This would usually be in the
winter months but some surface water forms in pockets after any
rain storm. The lakebed is soft with silt in places and gumboots
are recommended at any time if you propose to walk on the lakebed.
The former lake now also provides an important habitat for rare
ferns, mosses and orchids and various bird species. Care should be
taken not to disturb the wetland as you walk within it.
The listed
co-ordinates bring you to a parking point and entrance path to the
lakebed. Walk out onto the lakebed and imagine the forest that once
stood there. Proceed to each of the co-ordinates listed below and
answer the question posed (3 questions in all). You will need a GPS
and a tape measure (in metres). Email your answers to the
earthcache owner. Do not record your answers in your log. Also take
a photograph with your GPS displayed (include yourself or another
person if you wish) by one of the fossilized stumps. Upload this
photo with your log. The earthcache owner reserves the right to
delete logs that do not comply with these requests.
Question
1.
Go to S34 58.905,
E173 21.785.
What is the approximate
length of the exposed tree trunk located here? (in
metres)
Note the remanants of Kauri
gum still evident in the trunk.
Question 2.
Go to S34 58.869,
E173 21.802.
What is the approximate
diameter of the stump remains located here? (in metres to 1 decimal
place)
Question
3.
Go to S34 58.876,
E173 21.773
What is the approximate
elevation of the lakebed at this point? (in metres above sea
level)